Field of Invention
Various embodiments of the present disclosure relate to a method of controlling an external cavity laser, and more particularly, to a control method for a low-chirp operation of an external-cavity wavelength-tunable laser which is used for optical communication.
Description of Related Art
Generally, the most basic elements forming a LASER (Light Amplification by Stimulated Emission of Radiation) include a gain medium and a resonator having a pump for the supply of energy. To amplify radiated light through a stimulated emission process, a gain medium is absolutely necessary. The lasing wavelength band of the laser is determined depending on the kind of gain medium. Depending on the kind of gain medium, a gas laser, a dye laser, a solid-state layer, and so forth are representative examples of a laser that is relatively easily tunable in wavelength.
Research on a Wavelength Division Multiplexing (WDM)-based passive optical network (PON) (hereinafter, referred to as a ‘WDM-PON’), which is a network based on wavelength adjustment, has become appreciably more active. The WDM-PON may provide voice, data and broadcast convergence services.
In a WDM-PON, wavelengths assigned to respective subscribers are used for communication between a center office (CO) and the subscribers. Because the WDM-PON uses an exclusive wavelength for each subscriber, there are advantages in that security is excellent, massive communication service is possible, and the application of transmission technologies having different link rates and frame formats, etc. by subscribers or services is possible.
However, because the WDM-PON is a technology of multiplexing several wavelengths on a single optical fiber using the WDM technology, a number of different light sources, equal to the number of subscribers belonging to a single remote node (RN), are required. The production, installation and management of light sources for respective wavelengths imposes a huge financial burden on both users and business operators and thus is the chief obstacle to the commercialization of the WDM-PON. To overcome the foregoing problems, research on a method of using a wavelength-tunable light source device capable of selectively tuning the wavelength of a light source has become more active.